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Purpose The purpose of this study is to develop a additive manufacturing (AM) process for the fabrication of ionic polymer–metal composite (IPMC) devices with complex designs that would be time-consuming to replicate using conventional manual methods. These IPMC devices have considerable potential in electroactive polymers (EAPs) and soft actuators. Design/methodology/approach This paper presents a novel three–dimensional (3D) AM technique to develop IPMCs. Digital light processing (DLP) fabrication of soft EAPs was undertaken using a vat-based AM method, followed by deposition of cost-effective outer silver electrodes. Findings DLP-fabricated devices were compared to conventional Nafion™-117 devices. DLP layer-by-layer fabrication of these devices allowed for good resolution for a range of printed objects. Electrical actuation of the DLP-produced IPMCs showed tip displacements of up to 3 mm, and greater actuation was seen in the presence of lithium rather than magnesium cations. The IMPCs showed good ion exchange capacities, while electrochemical analysis showed the reversible formation and removal of AgCl layers in addition to ion movement. Practical implications The AM of these devices allows for rapid prototyping as well as potential use in the development of multiple degrees of freedom actuators and devices. Originality/value An original resin formulation was developed for DLP 3D printing. This formula is chemically distinct from the conventional Nafion™-117 membranes that can be purchased. Additionally, this method allows for the manufacture of complex objects that would be difficult to machine by hand. These findings are of value to both the fields of polymer chemistry and AM.

Almost all processed food comes packaged in either plastic, glass, metal, or paper and paperboard materials, and many packaging materials are disposed of after a single use (linear economy). Based on the concept of a circular economy, the recycling of food packaging materials has become one of the main targets for industries and regulators around the world. However, recycling presents particular challenges, mainly related to the recycled material composition, which determines its reusability, application, functionality, and chemical safety. In this latter matter, it has been demonstrated that the use of recycled food packaging materials increases the number and possible sources of substances that could be present in the packaging material, which is of concern as substances that can migrate into food and cause health hazards upon consumption. This review compiles information regarding substances detected in non-permanent food packaging materials, focusing mainly on plastics, paper, and paperboards. The compilation of literature studies (110 research articles) on the presence of intentionally added substances (IAS) and non-intentionally added substances (NIAS) in food packaging materials, their migration, toxicity, and dietary exposure has been summarized, evaluated, and discussed. In addition, current sustainable food packaging trends have been mentioned. Finally, approaches to reduce the presence, migration, and potential exposure to substances that have migrated from packaging materials into food have been reviewed.

Consumer perceptions and purchase behaviours are typically determined by phenolic influenced sensory attributes such as astringency, bitterness, and sourness. Marketing strategies would be more effective if machine learning methods assisted winemakers in understanding the chemical parameters that influence panellists' sensory evaluations of Pinot noir wines. Nowadays, feature selection methods such as random forest classifier and neighbourhood component analysis are utilised to select important factors. In the meantime, decision trees are utilised in regression or classification models as opposed to feature selection methods. In this study, decision trees were able to identify the relationships between sensory attributes and important chemical parameters in Pinot noir wines from diverse product extrinsic cues (regions of origin, vintages and price points) and novice panels. Decision trees not only could be utilised to build soft sensors but also work as effective feature selection methods, which could inspire winemakers to make proper Pinot noir wines. With the help of principal component analysis and scatter plots, it was discovered, for instance, that total phenolics, total flavanols, total flavan-3-ols, and total tannins in wines could considerably contribute to astringency, bitterness, and sourness and that total anthocyanin could contribute to clarity regardless of diverse Pinot noir wine or novice panels.

Glycosidically bound volatiles (GBVs) are flavorless compounds in fruits and may undergo hydrolysis during fruit maturation, storage, and processing, releasing free aglycones that are odor active. However, the contribution of glycosidic aglycones to the sensory attributes of fruits remains unclear. Herein, the key odor-active aglycones in tamarillo fruits were elucidated through the molecular sensory approach. We extracted GBVs from three cultivars of tamarillo fruits using solid-phase extraction and subsequently prepared aglycone isolates by enzymatic hydrolysis of GBVs. Gas chromatography-mass spectrometry-olfactometry (GC-MS-O) coupled with odor activity value (OAV) calculation, comparative aroma extract dilution analysis (cAEDA), and omission tests were used to identify key aromatic aglycones. A total of 42 odorants were determined by GC-MS-O analysis. Among them, trans-2,cis-6-nonadienal, 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF), linalool, 4-vinylguaiacol, geraniol, and α-terpineol showed high OAVs. The cultivar Amber had more aglycones with flavor dilution (FD) factors >16 than the Mulligan cultivar (27 vs 21, respectively), and the Laird's Large fruit showed the highest FD of 1024 for glycosidic DMHF. Omission tests indicated 14 aglycones as essential odorants related to GBVs in tamarillo fruits. Moreover, the enzymatic liberation of aglycones affected the sensory attributes of the tamarillo juice, resulting in an intensified odor profile with noticeable fruity and sweet notes. This study gives insights into the role of endogenous aroma during tamarillo-flavor perception, which lays the groundwork for developing tamarillo-based products with improved sensory properties.

This study investigated the free and glycosidic-bound volatiles in the juice samples of three tamarillo cultivars (i.e. Amber, Mulligan, and Laird's Large) that are widely grown in New Zealand. Juice samples were prepared from fruits at different ripening stages (green, middle, and ripe). Headspace solid-phase microextraction combined with gas chromatography-mass spectrometry was applied to analyze the free volatiles in the samples. A total of 20 free volatiles were detected. Among the samples, the ripe Mulligan juice gave the highest contents of free terpenoids (424 μg/L) and esters (691 μg/L). The glycosidic-bound volatiles were prepared by solid-phase extraction. The matrix effect was evaluated based on the recovery rate of analytes containing multiple aglycone classes. From the results, phenyl β-d-glucopyranoside was selected to compensate the matrix effect caused by insufficient acquisition of glycosidic volatiles during analyte preparation. In all the ripe-fruit juice samples, the aglycones 4-hydroxy-2,5-dimethyl-3(2H)-furanone and trans-2, cis-6-nonadienal were found to give high odor activity values. According to multivariate statistical analysis, 11 free volatiles and 22 glycosidic volatiles could be potentially applied as volatile makers to distinguish the juice samples. This study has provided a comprehensive understanding of the flavor chemistry of tamarillo juices, with a focus on the potential role of glycosidic aglycones as aroma contributors to tamarillo products.

Oxidative stress plays a pivotal role in the pathogenesis of many diseases, but there is no accurate measurement of oxidative stress or antioxidants that has utility in the clinical setting. Cyclic Voltammetry is an electrochemical technique that has been widely used for analyzing redox status in industrial and research settings. It has also recently been applied to assess the antioxidant status of in vivo biological samples. This systematic review identified 38 studies that used cyclic voltammetry to determine the change in antioxidant status in humans and animals. It focusses on the methods for sample preparation, processing and storage, experimental setup and techniques used to identify the antioxidants responsible for the voltammetric peaks. The aim is to provide key information to those intending to use cyclic voltammetry to measure antioxidants in biological samples in a clinical setting.

A new perspective is presented to investigate the sensorially relevant gas-phase concentrations of volatile compounds in wine. This is achieved by measuring the partition coefficients and matrix-phase concentrations of volatiles using static headspace-gas chromatography-ion mobility spectrometry (SHS-GC-IMS). Physicochemical properties that can contribute to the partition behaviors of ten volatile esters, such as hydrophobicity and matrix temperature, are also discussed. Partition coefficients are then linked to quantitative measurements to obtain partial pressures, which describes the availability of volatile compounds in the gas phase. The concept of partition coefficients and partial pressure have then been applied to a time series of aroma changes due to oxidation in commercial wines. As a follow-up study, a full factorial design was devised to inspect the impact of three common wine matrix components, namely, copper, polyphenols and ascorbic acid, on the partial pressure changes after 30-day oxidation treatment in either full-alcohol or low-alcohol simulated wine matrices. Interesting interactive effects between antioxidant behaviors and alcohol levels were elucidated, especially around the controversial use of ascorbic acid in winemaking. These results can guide winemakers who wish to minimize oxidative damage to wine aroma during wine storage or bulk transport, where ullage may be present or continual oxygen ingress may be occurring.

The milk and dairy industries are some of the most profitable sectors in many countries. This business requires close control of product quality and continuous testing to ensure the safety of the consumers. The potential risk of contaminants or degradation products and undesirable chemicals necessitates the use of fast, reliable detection tools to make immediate production decisions. This review covers studies on the application of electrochemical methods to milk (i.e., voltammetric and amperometric) to quantify different analytes, as reported over the last 10 to 15 years. The review covers a wide range of analytes, including allergens, antioxidants, organic compounds, nitrogen- and aldehyde containing compounds, biochemicals, heavy metals, hydrogen peroxide, nitrite, and endocrine disruptors. The review also examines pretreatment procedures applied to milk samples and the use of novel sensor materials. Final perspectives are provided on the future of cost-effective and easy-to-use electrochemical sensors and their advantages over conventional methods.

To achieve sustainability in the wine industry, by-products from winery operations are being diverted from waste streams and turned into beneficial use. Grape seed tannin (SeedT) and skin tannin (SkinT) extracts were used to modify the properties of gelatin films, and to prepare active/intelligent films. The SeedT extract showed a higher phenolic content (similar to 440 mg gallic acid (GA)/g extract) and antioxidant inhibition (similar to 20 %) than the SkinT extract (14 mg GA/g extract, 2 % antioxidant inhibition), while both extracts presented colour variations with an increase of solution pH. The addition of extracts into the gelatin formulation resulted in coloured and transparent films with lower wettability (water contact angle increased up to 92 degrees) and higher UV-light absorbance (secondary antioxidant function) properties. The films were capable of releasing tannins by up to 20 % which led to antioxidant inhibition values of up to 13 % (primary antioxidant function). The addition of SkinT tannins into the films provided the films with a pH indicator ability (intelligent function). The authors would like to thank the State Research Agency of Spain within the Juan de la Cierva - Incorporation action (IJC2019-039697I) and the Ministry of Business, Innovation and Employment (MBIE, Biocide Toolbox programme).

To find renewable and sustainable alternatives to reduce the severe environmental impact of single-use synthetic plastic packaging, glucose-crosslinked gelatin films containing different amounts of chitin nanowhiskers (CNWs) were prepared. CNWs were first prepared by acid hydrolysis of chitin from shrimps, and characterized (morphological and thermal properties), before their addition into film-forming formulations. The films were heat-treated to promote the chemical crosslinking Maillard reaction (MR), between glucose and gelatin. The films then became less soluble (from 100% to ∼10%), thermally more stable, had a notably improved UV–vis light absorption capacity, and presented significantly enhanced tensile strength (from 42 to 77 MPa) and Young's modulus (from 1476 to 2921 MPa), however, they also became less flexible (from 17% to 7%) and transparent. These property alterations were mainly related to changes in crystallinity, the MR and to a lesser extent, to the formation of noncovalent (electrostatic and hydrogen bonding) interactions between CNWs and gelatin. Furthermore, due to the formation of MR products, the films turned yellow/dark brown and released antioxidant compounds (inhibition ∼33%) while immersed in water, which gave the films their active properties (stabilization of free radicals). These films have considerable potential as reinforced active packaging films for renewable food packaging applications., The authors would like to thank the Ministry of Business, Innovation and Employment of New Zealand (MBIE, Biocide Toolbox programme) and the Spanish Ministry of Science and Innovation (projects PID2019-108361RB-I00 and AGL2017-84161-C2-1-R) for funding. A.E. thanks the State Research Agency of Spain within the Juan de la Cierva - Incorporation action (IJC2019-039697I).

A new quantitative method based on static headspace-gas chromatography-ion mobility spectrometry (SHS-GC-IMS) is proposed, which enables the simultaneous quantitation of multiple aroma compounds in wine. The method was first evaluated for its stability and the necessity of using internal standards as a quality control measure. The two major hurdles in applying GC-IMS in quantitation studies, namely, nonlinearity and multiple ion species, were also investigated using the Boltzmann function and generalized additive model (GAM) as potential solutions. Metrics characterizing the model performance, including root mean squared error, bias, limit of detection, limit of quantitation, repeatability, reproducibility, and recovery, were investigated. Both nonlinear fitting methods, Boltzmann function and GAM, were able to return desirable analytical outcomes with an acceptable range of error. Potential pitfalls that would cause inaccurate quantitation, that is, effects of ethanol content and competitive ionization, were also discussed. The performance of the SHS-GC-IMS method was subsequently compared against that of a currently established method, namely, GC-MS, using commercial wine samples. These findings provide an initial validation of a GC-IMS-based quantitation method, as well as a starting point for further enhancing the analytical scope of GC-IMS.

Rheological properties of gelatin-based solutions containing different concentrations of ribose and/or glycerol were assessed before electrospun mats were manufactured and their properties investigated. Characterization included morphology, X-ray diffraction, Fourier transform infrared, solubility, swelling, the release of Maillard reaction (MR) products and their antioxidant activity. Gelatin concentrations >= 16 % w/v favoured the formation of smooth nanofibres in the electrospinning process due to their higher viscosity than for gelatin concentrations

Glycosidically bound volatiles (GBVs) are flavorless compounds in fruits and may undergo hydrolysis during fruit maturation, storage, and processing, releasing free aglycones that are odor active. However, the contribution of glycosidic aglycones to the sensory attributes of fruits remains unclear. Herein, the key odor-active aglycones in tamarillo fruits were elucidated through the molecular sensory approach. We extracted GBVs from three cultivars of tamarillo fruits using solid-phase extraction and subsequently prepared aglycone isolates by enzymatic hydrolysis of GBVs. Gas chromatography-mass spectrometry-olfactometry (GC-MS-O) coupled with odor activity value (OAV) calculation, comparative aroma extract dilution analysis (cAEDA), and omission tests were used to identify key aromatic aglycones. A total of 42 odorants were determined by GC-MS-O analysis. Among them

Elemental sulphur is a common fungicide applied in vineyards before harvest, and has been found toincrease the production of desirable polyfunctional mercaptans, but also H2S and unwanted reductivesulphur aroma compounds. This paper investigates the effectiveness of oxygen and nitrogen sparging,applied during fermentation, on the removal of volatile sulphur compounds in Sauvignon blanc wines.Increasing the amount of elemental sulphur added to grapes after pressing, from nil to 10 to 100 mg/L,led to an increase in the formation of 3-mercaptohexanol (3MH), of 3-mercaptohexyl acetate (3MHA) forthe 10 mg/L additions only, and of some unwanted reductive compounds. Few changes were observed inthe concentrations of aroma compounds when the juices were sparged with nitrogen during fermentation.Additions of oxygen during fermentation led to some decrease in the concentration of polyfunctionalmercaptans for the 10 mg/L sulphur additions, but did not significantly remove reductive aroma compounds.Few differences were observed in the concentration of wine phenolics or of further wine aroma familieswith any of the treatments.

During its production wine can react with substantial amounts of aerial oxygen. Some oxidation can be beneficial, especially in red wine, but if allowed to occur in excess it is highly detrimental, making oxygen management an important aspect of wine making. The use of reduction potentials at platinum electrodes to measure the redox state of wines extends back over 80 years. The premise is that reductants in wine produce oxidized derivatives and the balance between the two determines the reduction potential, as in classical electrochemistry. As the detailed mechanism of wine oxidation becomes better understood, it is apparent that redox couples in wine do not function in this way. It is proposed that the observed potentials are mixed potentials largely due to ethanol oxidation coupled with oxygen reduction. Under low oxygen conditions, further redox couples can contribute to the mixed potential, both directly and via adsorption effects at the platinum electrode.

Phenolic and polymethoxylated flavones are important bioactive components in citrus fruit. Here, a rapid and sensitive method based on ultra-high performance liquid chromatography coupled with trip...

Spray drying-based microencapsulation has been applied to mask unpleasant odours and to protect bioactives in liquid based products. However, little research has been undertaken to explore how particle formation occurs during the drying process and the relationships associated with particle properties. This study aimed to fill the gap by investigating the relation of structure formation and properties of microencapsulated fermented noni juice (FNJ) powder containing maltodextrin (M1, 10–13 DE; M3, 17–20 DE) and gum acacia (GA) using a single droplet drying (SDD) technique, mimicking the spray drying process. The impact of wall materials and solids content on the structure formation and particle properties including solubility, hygroscopicity, particle size, bulk density and microstructure were predicted. The SDD process was designed to observe the drying process and to investigate the morphological changes of semi-dried particles by attaching a water droplet or by suspending the semi-dried/dried particle in the drying chamber without air flow. Microscopic analysis show that microstructures of the particles were influenced by the wall materials. M3 particles showed the best solubility, and are predicted to have higher bulk density and hygroscopicity than M1 and GA particles. The M1 particles displayed good solubility and had a larger particle size than the M3 particles. Particles containing GA had the lowest dissolution rate, and are expected to have the lowest bulk density among the three wall materials. Overall, this research has provided insight into particle structure formation and the properties of microencapsulated FNJ powders by the above hydrocolloid materials.

Two different methods for the synthesis of poly(3,4-ethylenedioxythiophene) (PEDOT) on gold electrodes are described, using electropolymerization of 3,4-ethylenedioxythiophene (EDOT) monomer in an aqueous and an organic solution. Cyclic voltammetry (CV) was used in the synthesis of PEDOT thin layers. Lithium perchlorate (LiClO4) was used as a dopant in both aqueous (aqueous/acetonitrile (ACN)) and organic (propylene carbonate (PC)) solvent systems. After the PEDOT layer was created in the organic system, the electrode surface was acclimatized by successive cycling in an aqueous solution for use as a sensor for aqueous samples. The use of an aqueous-based electropolymerization method has the potential benefit of removing the acclimatization step to have a shorter sensor preparation time. Although the aqueous method is more economical and environmentally friendly than the organic solvent method, superior PEDOT formation is obtained in the organic solution. The resulting PEDOT electrode surfaces were characterized by scanning electron microscopy (SEM), which showed the constant growth of PEDOT during electropolymerization from the organic PC solution, with rapid fractal-type growth on gold (Au) microelectrodes.

Sauvignon blanc is the most important grape cultivar within the New Zealand wine industry, and wines from the Marlborough region are renowned for their intense aromas including tropical, passionfruit, and green capsicum. Quality Sauvignon blanc wines are usually made from free run juice, although press fractions can be included. The chemical aroma composition and sensory profiles of two wine sets made from three press fractions (free run, light press and heavy press) were compared. The compounds 3-mercaptohexan-1-ol and 3-mercaptohexyl acetate were found to decrease between free run and heavily pressed wines while hexyl acetate, hexanol, and benzyl alcohol increased. The accompanying sensory analysis showed that free run wines were marked by aromas of Passionfruit/sweaty, Boxwood and Fresh green capsicum, while the heavy pressed wines were described by French vanilla/bourbon, Floral and Banana lolly attributes, consistent with the aroma chemical composition.

This study investigated the free and glycosidic-bound volatiles in the juice samples of three tamarillo cultivars (i.e.

This work reports an environmentally benign and readily scalable process for production of akaganeite (β-FeOOH) nanocomposites by using abundant gallic acid or grape seed tannins and urea. Influences from those phytochemicals on the properties of β-FeOOH nanocomposites were investigated by X-ray powder diffraction, Fourier transform infrared spectroscopy, Thermogravimetric analysis, Scanning electron microscopy, Transmission electron microscopy, UV–Vis spectroscopy and Photoluminescence. The addition of 0.1% (w/v) grape seed tannins or gallic acid (640 mg L−1) solution yielded single-crystalline β-FeOOH nanocomposites with reduced dimensions, increased porosities and BET surface area, and no oxidized impurities such as hematite (Fe2O3) were formed. The added grape seed tannins (S0.8) or gallic acid together with less urea (0.8 M) produced β-FeOOH nanocomposites with higher activities as peroxidase mimics compared to those prepared with only urea (C0.8). Moreover, S0.8 was more efficient in methylene blue (MB) discoloration compared to C0.8 at all three pH values of 4, 7 and 11, and the S0.8-mediated MB degradation pathways at pH 4 and 7 were different from those at pH 11 due to the generation of different predominant oxidants. The overall MB discoloration efficacies by S0.8 at pH 4, 7 and 11 were combinative effects of both physical adsorption and chemical reactions. These β-FeOOH nanocomposites possess great potential as peroxidase mimics for facile monitoring of excess hydrogen peroxide and applications in environmental remediation.

The analytical scope of static headspace-gas chromatography-ion mobility spectrometry (SHS-GC-IMS) was applied to wine aroma analysis for the first time. The method parameters were first fine-tuned to achieve optimal analytical results, before the method stability was demonstrated, in terms of repeatability and reproducibility. Succinct qualitative identification of compounds was also realized, with the identification of several volatiles that have seldom been described previously in Sauvignon Blanc wine, such as methyl acetate, ethyl formate, and amyl acetate. Using the SHS-GC-IMS data in an untargeted approach, computer modeling of large datasets was applied to link aroma chemistry via prediction models to wine sensory quality gradings. Six machine learning models were compared, and artificial neural network (ANN) returned the most promising performance with a prediction accuracy of 95.4%. Despite its inherent complexity, the ANN model offered intriguing insights on the influential volatiles that correlated well with higher and lower sensory gradings. These findings could, in the future, guide winemakers in establishing wine quality, particularly during blending operations prior to bottling.

8.8 MT of food wastes are annually generated in the EU, in part due to the lack of real-time food freshness information provided by current food data labels. To address this issue, intelligent packaging strategies are being developed. In this study, in search of new natural and food grade pH-indicators, color stability and variability of curcumin (E−100), betanin (E−162), and anthocyanin (E−163) containing food colorants were studied in solution under different food storage conditions and pHs by light absorbance, color, pH and turbidity measurements. E−100 provided color variations (yellow/brown-yellow) at pH > 9 and was particularly photosensitive since a color loss of 67% was observed after 1 day of storage. E−162 and E−163 colorants, however, were thermosensitive and showed significant lower loss of color (30%) after 28 days of storage. E−163, especially, presented a broader color response (red-purple-blue-green) over a wider pH range. Furthermore, color variations at different pHs were dependent upon colorant type and concentration. A.E. thanks the Ministry of Science, Innovation and Universities (Juan de la Cierva contract).

In this paper, we report on the application of the static headspace-gas chromatography-ion mobility spectrometry (SHS-GC-IMS) instrument in the field of wine aroma analysis and its potential in constructing a prediction model for the quality gradings of wines. The easy-to-operate, cost effective SHS-GC-IMS instrument was innovatively used for a non-targeted search for volatile compounds in Sauvignon Blanc wine, with the identification of volatiles seldom before reported. The wine aroma profile acquired by the instrument was organically and innovatively combined with advanced classification models, inspired by the computer science community, to produce high classification accuracy in terms of wine quality gradings. Useful insights were also extracted by using advanced interpretation methods on complex models to learn the important volatiles correlated with wine quality grading.

The antioxidants sulfur dioxide (50 ppm) and ascorbic acid (100 ppm) were added to grapes soon after harvest at crushing. The chemical composition and sensory profile of Sauvignon Blanc, Pinot Gris and Chardonnay wines were examined, made from grapes collected at three different sites for each variety. With good antioxidant protection of the juices, reflected in low absorbances at 420 nm, remarkable increases in the polyfunctional mercaptans, 3-mercaptohexanol (3MH) and its acetate ester (3MHA), were seen in the wines. Moreover, high levels of these compounds were produced in the Pinot Gris and Chardonnay wines, equally high as with Sauvignon Blanc. The Pinot Gris wines maintained varietal characteristics in sensory profiles, even with high levels of polyfunctional mercaptans. When elemental sulfur was included with the grapes at crushing, extra increases in polyfunctional mercaptans were observed. However, this led to the production of unwanted reductive aroma compounds in some wines.

Anthocyanins scavenge harmful reactive oxygen species (ROS), and may provide antioxidative protection within plant cells. For the shade species Elatostema rugosum A. Cunn., it was recently established that red-leaved morphs held a significant antioxidant advantage over green morphs. It is not known whether anthocyanins confer the same protection in sun species that are exposed to elevated levels of irradiation and thus greater photooxidative stress. Quintinia serrata A. Cunn., a canopy tree species, is polymorphic for anthocyanin expression. Levels of antioxidants in leaves of red and green morphs of Q. serrata were identified, and activities quantified using enzymatic and α,α-diphenyl-β-picrylhydrazyl (DPPH) assays and cyclic voltammetry. Both morphs contained similar levels of superoxide dismutase, catalase, ascorbic peroxidase and hydroxycinnamic acids, and showed similar ranges in DPPH scavenging activity and voltammetric profiles. Anthocyanin concentrations increased with leaf age in red morphs and were positively correlated with the extent of DPPH scavenging. However, hydroxycinnamic acids were the most active methanol-extractable fraction in both morphs, contributing 27% more to the overall low-molecular-weight antioxidant pool in the green morph than in the red. We conclude that anthocyanin biosynthesis can enhance, but is not a prerequisite for, oxidative protection in Q. serrata leaves. The possibility that anthocyanins provide a versatile mechanism for photoprotection is discussed.

Key metabolites and flavour-regulation pathways in tamarillo were investigated to explore the development of free and glycosylated volatile organic compounds (VOCs) during fruit maturation. The concentrations of free and bound VOCs were determined by gas chromatography-mass spectrometry analysis. Changes of physical parameters, concentrations of flavour precursors, and activities of key endogenous enzymes were also monitored. A total of 22 free VOCs were identified with C6 alcohols and esters being the major compounds. From the 83 glycosylated VOCs detected, phenols and terpenoids were the dominant components. The concentration of total bound VOCs increased up to 4 times during fruit ripening. Lipoxygenase pathway is confirmed as an important biosynthetic mechanism for the generation of free and glycosylated VOCs during tamarillo ripening. This biosynthesis pathway is highly correlated with the activities of key enzymes and the contents of substrates, especially linolenic acid (p 0.05 or p 0.01).

Electroactive, elastomeric, microfiber mats that show controllable pore size variation upon electrochemical stimulation are produced from semi-interpenetrating polymer networks (s-IPNs). This type of porous, elastomeric scaffolds that are mechanically dynamic under electrochemical stimuli could find new applications in stretchable electronics, (bio)filtration, soft robotics and stimulation of biological cells. These microfiber mats are prepared in two simple steps. Firstly, a mixture of high molecular weight nitrile butadiene rubber (NBR) and cross-linking agent, poly(ethylene glycol)dimethylacrylate are electrospun with in situ cross-linking. Secondly, a conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) is embedded into the electrospun fibres by oxidative chemical polymerization of EDOT-swollen microfiber mats. This two-step process affords robust, highly flexible and conductive s-IPN microfiber mats. The microfiber mat undergoes a controllable pore size variation upon applying an electrochemical stimulus in the form of a reduction–oxidation cycle to the mats in an electrolyte. The maximum average pore size variation, measured in situ using confocal microscopy, is 25%, achieved in 1 M lithium bis-trifluoromethanesulfonimide (LiTFSI) in propylene carbonate (PC) for a potential step between +0.6 V and −0.5 V (vs. Ag wire). These mats also show pore size variation in a biologically compatible solution, phosphate buffered saline.

A new methodology to increase the polypyrrole (PPy) bilayer actuation displacement is presented, based on photo-activated dopants generating secondary charges. Two dopants, dodecyl benzenesulfonate (DBS) and the photo-active dopant 2-diazo-1-naphthol-5-sulfonic acid (DNSA), were compared in this study. PPy/DBS, PPy/DBS-DNSA and PPy/DNSA bilayers on polyethylene terephthalate were formed and their actuation properties in aqueous electrolyte were investigated applying cyclic voltammetry and square wave potential steps. Exposure to solar irradiation increased PPy/DBS-DNSA and PPy/DNSA bilayer bending displacements by two and three times, respectively, accompanied by increased charge density during the reversible redox cycles. UV–vis and Fourier transform infrared (FTIR) measurements were also performed to follow the photo reaction of the photo-active dopants.

Carbon nanomaterials possess superb properties and have contributed considerably to the advancement of integrated point-of-care chemical and biological sensing devices. Graphene has been widely researched as a signal transducing and sensing material. Here, a grass-like laser-scribed graphene (LSG) was synthesized by direct laser induction on common polyimide plastics. The resulting LSG grass was employed as a disposable electrochemical sensor for the detection of three neurotransmitters, dopamine (DA), epinephrine (EP), and norepinephrine (NE), and in the presence of uric acid and ascorbic acid as potential interferants, using differential pulse voltammetry and cyclic voltammetry. The LSG grass sensor achieved sensitivities of 0.243, 0.067, and 0.110 μA μM-1 for DA, EP, and NE, respectively, whereas the limits of detection were 0.43, 1.1, and 1.3 μM, respectively. The selectivity of LSG grass was excellent for competing biomarkers with high structural similarity (EP vs NE and EP vs DA). The exceptional performance of LSG grass for DA, EP, and NE detection holds a promising future for carbon nanomaterial sensors with unique surface morphologies.

The fabrication of a novel, and highly selective electrochemical sensor based on a poly(3,4-ethylenedioxythiophene) (PEDOT) modified laser scribed graphene (LSG), and detection of dopamine (DA) in the presence of ascorbic acid (AA) and uric acid (UA) is described. LSG electrodes were produced with a 3-dimensional macro-porous network and large electrochemically-active surface area via direct laser writing on polyimide sheets. PEDOT was electrodeposited on the LSG electrode, and the physical properties of the obtained films were characterized by scanning electron microscopy (SEM) and energy dispersive X-ray diffraction microanalysis (EDAX). The modified electrodes were applied for the determination of DA in the presence of AA and UA using cyclic voltammetry (CV), and differential pulse voltammetry (DPV) techniques. The linear range for dopamine detection was found to be 1–150 µM with a sensitivity of 0.220 ± 0.011 µA μM−1 and a detection limit of 0.33 µM; superior values to those obtained without PEDOT. For the first time, PEDOT-modified LSG have been fabricated and assessed for high-performance dopamine sensing using cost-effective, disposable electrodes, with potential for development in further sensing applications.

Here we present a sensitive and selective electrochemical sensor that has been developed for the analysis of uric acid and ascorbic acid in milk with minimum interference from each other. A conducting polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), was prepared electrochemically as a thin layer on a glassy carbon electrode and then acclimatized to an aqueous buffer before sample analysis. The modified sensor showed an excellent catalytic response towards the oxidation of uric acid, with an anodic peak during cyclic voltammograms at around 350 mV (Ag/AgCl), taken at pH 6.6 as typical of untreated milk samples. A small peak due to ascorbic acid was located close to 0 mV, enabling the simultaneous detection of the two antioxidants. A stronger response for ascorbic acid was produced at pH 3, a pH value obtained after treating milk with acids to remove protein material prior to HPLC analysis. The electrochemical oxidation of uric acid at the modified electrode involved pre-adsorption of uric acid and a form of stripping voltammetry. This was not the case with ascorbic acid where the oxidation proceeded under diffusion control, with a diffusion coefficient of 6.9 × 10−6 cm2 s−1 obtained from cyclic voltammograms. Good linear relationships between peak current intensities and concentrations were obtained in the range of 6–100 μM for uric acid and 30–500 μM for ascorbic acid. The sensitivity and limit of detection (S/N = 3) for the PEDOT-modified electrode were 2.5 μA μM−1 cm−2 and 7 μM for uric acid, and 0.6 μA μM−1 cm−2 and 45 μM for ascorbic acid, respectively. The newly developed sensor was successfully applied to milk samples for a fast voltammetric determination of uric acid and ascorbic acid concentration.